In conventional vehicle behavior controlling apparatuses, there are those that controls braking force generated on wheels so as to control braking force of the wheels according to the driving condition of the vehicle, regardless of a driver's intention during when the vehicle travels, whereby stability during the travel of the vehicle is secured. As the control of the behavior of the vehicle described above, when a control deviation of a yaw rate exceeds a predetermined threshold value during the turn of the vehicle, braking force is generated on a front wheel at the outside of the curve, whereby the yaw rate is reduced to stabilize the behavior.
In a brake device used for stabilizing the behavior of the vehicle as described above, oil pressure is generated by a hydraulic pump, and various valves are operated to apply the oil pressure generated by the hydraulic pump to a wheel cylinder mounted in the vicinity of a wheel, whereby braking force is generated on the wheel. However, when the braking force is generated on the wheel, it is necessary to start the hydraulic pump or operate the valves. Therefore, a time lag tends to occur until the braking force is actually generated after the instruction of generating the braking force.
On the other hand, when braking force is generated on the wheel in order to stabilize the behavior by the vehicle behavior controlling apparatus, braking force should be generated as rapidly as possible in order to stabilize the unstable behavior such as spin mode or the behavior of the vehicle not caused by the driving operation. When the braking force is delayed, the control for stabilization is also delayed. Therefore, some of the conventional vehicle behavior controlling apparatuses prevent the delay in the braking force for stabilizing the behavior of the vehicle.
For example, in a vehicle stabilized driving dynamic control apparatus described in Patent Literature 1, when it is estimated that braking force is generated on a wheel in order to stabilize the behavior during the turn of the vehicle, preparatory brake pressure that is a brake oil pressure of a low level is applied beforehand to the wheel on which the braking force is estimated to be generated. With this process, when braking force is generated on the wheel, such as the front wheel at the outside of a curve, which can stabilize the behavior through the generation of the braking force, in case where the behavior of the vehicle becomes unstable during the turn, the oil pressure, which is to be exerted on the wheel cylinder of the wheel, can be increased in a short period to allow effective braking force to be generated as rapidly as possible, whereby the behavior can be stabilized.
There may be the case in which a so-called turning-back steering, where a vehicle turns in one of the right and left directions and then, turns in a reverse direction, such as the case of changing a driving lane or fishhook steering, is executed during the travel of the vehicle. The unstable behavior such as spin mode might occur not only when the first steering is executed but also when the second steering in the turning-back steering is executed. Therefore, in the vehicle stabilized driving dynamic control apparatus described in Patent Literature 1, the preparatory brake pressure is applied even when the turning-back steering is executed. Specifically, when it is determined that the vehicle is steered in one of the right and left directions, and then, steered in the reverse direction, the preparatory brake pressure is applied to the front wheel at the outside in the turning direction of the second steering. With this, the braking force is generated by the front wheel at the outside as rapidly as possible, even if the behavior of the vehicle becomes unstable in the second steering, whereby the behavior can be stabilized.